In modern minimally invasive surgery, the instruments needed for the procedure are introduced into the inside of the body, for example into the abdominal cavity, through cannulae and guided under the control of a likewise introduced endoscope or under X-ray observation and actuated for individual operation steps. Such operations techniques are used for example in laparoscopic cholecystectomy and appendectomy.
Intraabdominal sutures must be provided in these and similar operations. The sutures are created using special surgical needles which are held from outside the body with a needle holder introduced through a cannula and guided by the operator. Such needle holders are provided with two clamping jaws which are movable towards each other to grasp a needle in the manner of forceps between the clamping jaws. One or both of the clamping jaws are opened and closed by a push- or pull-rod guided in the instrument tube of the needle holder.
The position at which the needle lies between the clamping jaws is not predetermined, i.e. the needle can lie well to the rear, near the axis of rotation of the clamping jaw, so that when the jaws grasp the needle, they remain relatively widely opened. Or the needle can lie well forward, near the distal ends of the clamping jaws, so that when the jaws grasp the needle, they are largely closed. Efforts must be made to ensure that the force exerted by the clamping jaws is as independent as possible from the extent to which the grip or the clamping jaws are closed.
Another disadvantage with such holders or forceps is that, because the grip is very large in relation to the clamping jaws, it is very difficult for the user to measure the force exerted on the clamping jaws. The clamping jaws are frequently pressed against each other with too great a contact pressure if the operator closes a gripping member, so that the clamping jaws encounter a resistance lying between them. This can easily result in damage to the clamping jaws, to their bearings or in the transmission of force, and the life of the instrument is reduced overall through overloading. It is known in this regard to provide force-limiting mechanisms in the transmission from the grip onto the clamping jaws.
With the medical forceps described in DE-OS 40 10 775 with a fixed and a swivellable jaw part, a grip arrangement with a fixed and a swivellable grip part is provided. The movement of the swivellable rip part is transmitted via a push- or pull-rod onto the swivellable jaw part. To limit the compressive force at the mouth parts, the swivellable grip part is divided into two parts which are connected to each other by a bending spring element. As the bending spring element is deflected when the jaw parts encounter resistance, the force onto the jaw parts is limited even if the grip is closed to the greatest possible extent.